Einiosaurus (“buffalo lizard”) was part of a branch of the centrosaurs known as the Pachyrhinosaurini, a group with especially elaborate nose ornamentation.
Living about 74 million years ago in Montana, USA, it’s known from hundreds of bones representing over fifteen different individuals of varying ages. It had little-to-no brow horns, and two long spikes at the top of its frill – but also one of the most unusual-looking nose horns of all the ceratopsids, curving strongly forward and downward into a large hooked shape.
The juvenile remains show evidence of very rapid growth during their first few years of life, only starting to slow down around age 3-5, suggesting that was the point they began to reach reproductive maturity. The largest specimens are estimated to have measured about 4.5m long (14′9″), although they appear to have been subadults who still hadn’t quite reached their full size.